This invention concerns an injection molding nozzle for an injection mold and more particularly a heatable injection molding nozzle comprising a tip insert, a mold insert, and a displaceable needle having a cylindrical needle tip fitting with small clearance into a cylindrical end portion of a gating of the mold.
In a known injection molding nozzle of this kind disclosed in published French Patent Application No. FR-A-2,537,497, a conical tip insert freely protrudes into the mold insert of the nozzle without being in contact with the insert. This approach has been selected in order to keep the heat transfer low between the mold insert and the tip insert at the location of the outlet of the molding material. However, this solution has the disadvantage that a hollow space remains in the outlet conduit between the tip insert and the mold insert where the material to be molded during molding can enter and will remain therein. This remaining material impairs or slows down a rapid change of the molding material, especially a color change. In spite of this disadvantage, a relatively intensive heat transfer between the tip insert and the mold insert cannot be avoided. The centering of the nozzle needle in the mold gating is deficient since the cylindrical needle tip is not precisely guided with respect to the cylindrical end region of the gate opening so that gripping of the tip will occur.
It is an object of the present invention to avoid the drawbacks discussed above and to obtain additional advantages.